Figure 3-4. Power Supply Block Diagram

TM 11-5820-919-12

Figure 3-4. Power Supply Block Diagram

shaft noticeable with temperature. The TCXO outputs

5MHZ LO goes to a frequency divider w here it is

3-32. The hydrid accepts signals from other modules in

divided to 10 KHz. The 1 kHz frequency is used by the

the radio set and generates the following alarm signals:

modulator/demodulator for cw key operation or for fault

(1) Low Battery Indicator (2) Tune In Progress and (3)

indication signals 3-29. The 5 MHz LO is also applied

Tune Fault. The Low Battery Indicator is set off if the

to a frequency multiplier which generates 70and 80MHz

+28v On from the control panel drops bellow +20v. The

harmonics. The harmonics are filtered by 70and 80-MHz

Tune In Progress indicates that the antenna tun er is

bandpass filters and routed to the limiter. The Sideband

automatically matching the antenna to the radio set at

Select signal is applied to the limiter. If the sideband

the selected frequency. The Alarm signal is routed from

select switch is set to LS B, then the limiter sends 80

the alarm circuits to the audio circuits to develop audible

MHz LO to the modulator/demodulator. If USB is

tones which ar e applied to the Rev Audio:

selected, the limiter sends 70 MHz LO to the

modulator/demodulator.

1. When battery power drops below +20v , a

clicking sound is heard in the handset.

3-30. The Frequency Select from the control panel

2. If the antenna fails to complete a tune cycle

determines the output of the 77-105 MHz Lo signal

within 12 seconds. a repetitive beeping 1-kHz tone will

;using a dual phase -locked loop. A dual loop is faster

be heard in the handset (Tune Fault).

than a single loop phase locking system. A voltage

2.64 thru 9v) from the phase-locked loop tunes the

The tone will also be heard if a frequency below 2 MHz is

voltage-controlled oscillator (VCO) to a higher or lower

selected.

frequency.

The 77-105 MHz LO signal is divided in

the dual phase-locked loop ac cording to the Frequency

3. During the time that the antenna turner is in a

Select setting until it is 10 kHz. It is compared against

tune cycle. a steady, low-volume (I-kHz) tone is heard in

the 10 kHz from the frequency divider to provide the

the handset (Tune In Progress).

locking action. If the divided 77-105 MHz LO is above or

below 10 kHz.

the VCO's output is automatically

adjusted.

3-33. The audio circuits control the level of the transmit

signal and the gain of the receive signal . The mode

3-31. MNODULATOR/DEMODULATOR (Figure 3-6)

signal from the control panel inhibits transmit operation if

The

modulator/demodulator

performs

frequency

V_RCV is selected. the 1 KHz from the synthesizer is

conversion for both transmit and receive operation. The

switched on and off by the cw key. In transmit

audio control ;hydrid contains control circuits, while the

operation, the Xmt Audio Frequency is routed from the

three converters perform the frequency conversion. The

audio contro9l hydrid to the third converter, it mixes with

hydrid outputs the Xmt/Rev Control signal which

either 70 or 80 MHz, depending on the sideband

determines whether the racdxio0 set is in transmit or

selection (80 MHz for LSB,

70MHz for Usb

receive operation.

3-7